[Nix-dev] fixing ghc-pkg update

[Marc Weber]

Excerpts from roconnor's message of Fri Jan 07 03:49:37 +0100 2011:
> Why would you want to use the installer for cabal as opposed to hack-nix? 
MAybe because its smarter. Its not using brute force. It takes more
possibilities into account. Yet hack-nix got the job done for me in the
past.

There are more issues. In the past I found cases where --package-conf
args are passed more than once (I think it is when using cabal build or
such). also ghc-pkg list does not show the ghc installed packages.

On the other side hack-nix can cope with gtk2hs (which cabal couldn't in
the past.

There is an alternative to the current implementation: Using
GHC_PACKAGE_PATH to pass libraries to ghc. However you have to patch
cabal. (I mantained a patch in the past doing so - but I got tired of
keeping it up to date because using $PATH to find libraries satisfied my
needs even though I first thought it was a bad choice).
It actually is if you put ghc libraries into your main environment. So I
don't do that.

> I don't know the answer to that, but we should strive to make cabal work 

Do you mind talking about the use case which doesn't work for you
currently?

Marc Weber